A rear wheel suspension system having a composite link axle, the links of which are connected to one another by a torsion rod, is known, for example, from DE 37 07 162 A1. A rear wheel suspension system of this type generally has a left-hand and a right-hand longitudinal link which are articulated with their front ends on the vehicle body by means of rubber elements, with the result that they can perform a vertical pivoting movement with regard to a roadway plane, and a torsion rod which connects the center regions of the longitudinal links to one another. The rear wheels are supported at the rear ends of the longitudinal links, with the result that vertical movements of the rear wheels relative to one another on account of roadway unevennesses are delimited by the torsional counterforce of the torsion rod.
As is known, composite link axles of this type tend to oversteer under lateral force. In order to counteract this oversteer tendency and to improve the driving behavior of the motor vehicle when driving around bends, DE 37 07 162 A1 proposes rotating the pivoting axes of the pivoting bearings by a predefined yaw angle in a horizontal plane which is parallel to the roadway plane, with the result that the pivoting axes intersect in front of the connecting line between the body-side ends of the longitudinal links. The pivoting bearings are set in this way to control the toe of the rear wheels as a function of a lateral force which acts on the rear wheels when driving around bends (toe control).
Furthermore, DE 35 24 763 A1 discloses a motor vehicle rear axle, in which the body-side pivoting bearings of wheel control elements carry the wheels are arranged and configured elastically or elastokinematically to counteract a tendency of the wheel control elements to yield in the direction of oversteer when driving around bends under the action of lateral forces that act on the wheels. In particular, the pivoting axes of the pivoting bearings are guided in each case in elastomeric elements and in a slotted guide that extends at an angle obliquely with respect to the vehicle longitudinal axis.
DE 36 36 878 A1 describes an axle suspension system for motor vehicles which consists of two longitudinal links, that are articulated pivotably on the vehicle body and carry the vehicle wheels. The ends of a flexurally rigid but torsionally soft transverse strut are connected to the two longitudinal links in an angularly rigid manner. In particular, the bearing axes of the link bearings are set obliquely to the front in such a way that their extensions intersect in the vehicle center plane and in front of the link bearings.
Finally, DE 10 2008 035 625 A1 describes a motor vehicle rear axle as composite link axle with two wheel-carrying, rigid longitudinal links, that are articulated elastically on the vehicle body, and a flexurally stiff but torsionally soft transverse strut. The pivoting axes of the pivoting bearings of the rear axle are set obliquely to the front in relation to a connecting line between the pivoting bearings.
The kinematic behavior of composite link axles is fixed by a few design parameters. The behavior is fixed, in particular, by the position of the elastomeric bearing bushes which are preferably arranged in the body-side pivoting bearings and by the shear center height of the torsion profile. The orientation of the pivoting bearing bushes plays an important role on account of the elastic properties of the bearing bushes. As a rule, the elastomeric bearing bushes are configured to be substantially softer in the axial direction than in the radial direction.
Controlling the roll steer of the composite link axle during rolling, wheel camber change during rolling and the roll center height are the most important parameters for rear wheel suspension systems. These parameters cannot be set independently of one another. With the given design parameters, a partially undesired elevation of the roll center results from an increase in the roll control and an increase in the wheel camber change during rolling.